# What You'll Need:
→ Sourdough Starter
01 - 3.5 oz active sourdough starter (100% hydration)
→ Dough
02 - 14 oz bread flour
03 - 10 fl oz lukewarm water
04 - 0.35 oz fine sea salt
05 - 0.68 fl oz extra-virgin olive oil
→ Topping
06 - 2 medium yellow onions, thinly sliced
07 - 1 tbsp olive oil
08 - 1 tsp flaky sea salt
09 - 1 tsp fresh rosemary leaves
10 - Freshly ground black pepper
# Method:
01 - In a large bowl, combine sourdough starter, bread flour, and lukewarm water until a shaggy dough forms. Cover and rest for 30 minutes.
02 - Add fine sea salt and extra-virgin olive oil to the dough. Mix thoroughly until fully incorporated.
03 - Over 2 hours, perform 3 to 4 sets of stretch and folds at 30-minute intervals to develop gluten strength. Perform each set by stretching the dough from edges toward center.
04 - Cover the bowl and allow the dough to rise at room temperature for 6 to 8 hours until doubled in volume.
05 - Generously oil a 9x13-inch baking pan. Transfer the dough to the pan with minimal deflation. Using oiled fingers, gently stretch and press the dough to fill the pan evenly.
06 - Cover the pan and refrigerate for 8 to 12 hours overnight to develop flavor complexity and achieve superior texture.
07 - While dough chills, heat 1 tbsp olive oil in a skillet over medium-low heat. Add sliced onions and cook with occasional stirring for 20 to 25 minutes until deeply golden, tender, and caramelized. Cool completely before use.
08 - Remove dough from refrigeration and allow it to reach room temperature, approximately 1 hour, to ensure even oven spring.
09 - Preheat oven to 425°F. Using your fingertips, create dimples across the dough surface. Drizzle with additional olive oil, then distribute caramelized onions, flaky sea salt, rosemary, and black pepper evenly over the surface.
10 - Bake for 25 to 30 minutes until the focaccia achieves a deep golden-brown color with crisp edges.
11 - Allow the focaccia to cool slightly before slicing and serving warm.